1. Field of the Invention
The present invention relates generally to communication over an Ethernet-Class network and, more specifically to communication over a power line network.
2. Background Art
The vision of the networked home has driven many a business plan, but product offerings to date have been too limited in capability or in market potential to achieve the dream. Home networking is different than networking in the workplace. The applications are different, the traffic patterns are different, and the media available to carry the data are different. Certainly home networking users will want to transfer files between their computers and share peripherals such as printers. They will want gateways to broadband access so they can share their Internet connection between multiple devices. Users will also want other services, such as voice-over-IP (VoIP), streaming media for entertainment, and support for multi-player networked games.
While some newer houses are wired with cables suitable for Ethernet, most are not. Thus, if choices for home network physical media are limited to phone wiring, wireless, and power line, there are a mixed bag of attributes.
There has been a proliferation of wireless networking and related components in recent years. However, wireless communication suffers from limited range and less than universal coverage, i.e. certain areas of the home cannot communicate with others. These issues are particularly prominent in certain types of construction that result in poor signal propagation, such as those using steel frame and brick walls. Solutions to these issues are expensive and complex, and require some technical acumen not available to the average homeowner.
Although telephone line networking may at first appear to be a solution, many households lack phone jacks at convenient locations to achieve the foreseeable benefits of home networking. For instance, some older houses may only have one phone jack located in the kitchen for use in the kitchen and other living areas (e.g. living room, family room, etc). Thus, it may be inconvenient or messy to provide network connections to remote devices. This picture is particularly unfavorable in less developed countries. Power plugs, on the other hand, are located in almost every room in the home, and some homes have multiple power outlets located on every wall of every room. The power line appears to be the most difficult medium of these three for communication, but it does have two appealing attributes. First, as with phone lines, no RF conversion hardware is needed and, thus, the cost can be low compared to wireless solutions. But more importantly, power outlets are almost everywhere someone might want to use a networked device at home.
The power line medium is a harsh environment for communication. For instance, the channel between any two outlets in a home has the transfer function of an extremely complicated transmission line network with many unterminated stubs and some having terminating loads of varying impedance. Such a network has an amplitude and phase response that varies widely with frequency. At some frequencies the transmitted signal may arrive at the receiver with relatively little loss, while at other frequencies it may be driven below the noise floor. Worse, the transfer function can change with time. This might happen because the homeowner has plugged a new device into the power line, or if some of the devices plugged into the network have time-varying impedance. As a result, the transfer function of the channel between outlet pairs may vary over a wide range. In some cases, a broad swath of bandwidth may be suitable for high quality transmission, while in other cases the channel may have a limited capacity to carry data.
With many power outlets available for plugging in a new networked device at any time, the issues involving the management and coordination of the networked devices bring about concerns regarding the overall throughput of the network, Quality of Service (QoS) for each connection, authentication, coordination, and sharing of the network resources. Accordingly, there is a need in the art for management and coordination schemes that can effectively and efficiently address such concerns.